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TABLE OF CONTENT
 INTRODUCTION
 General information on supercritical fluids
 Supercritical fluid extraction
 Supercritical fluid chromatography
 Application
 conclusion
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INTRODUCTION
 The use of supercritical fluids in various scientific and industrial applications
has a rich and evolving history. From their discovery in the 19th century to
their modern role in green chemistry, pharmaceuticals, and environmental
science, the story of supercritical fluids is one of continuous innovation and
expanding possibilities.
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What is a supercritical fluid?
 Deffinition : supercritical fluid is any substance
at a temperature and pressure above its critical point.
Phase Diagram
 Example : Commonly used supercritical fluids are
and .
 Critical point : represents the highest temperature and
pressure at which the substance, can exist as a vapor
and liquid in equilibrium.
Fig 1: Phase diagram of Supercritical fluid,
Region Characteristics of Supercritical fluids
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Properties of SCF
 Combine propertise of a gases and liquids in a intrigning manner.
 Solvent power similar to light hydrocarbons for most of the solutes.
 Solubility increases with increasing density (that is with increasing pressure).
 The fluid are commonly miscible with permanent gases (e.g. N2, H2) and this
leads to much higher concentration off dissolved gases, than can be archived
in conventional solvents
In general terms, supercritical fluid have properties, betweeen those of a gas and
a liquid.
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Common supercritical fluid:
Carbon dioxide is commonly used due to :
 Environmentally freindly and generally recognized as safe by the food and dring
administration (FDA).
 non toxique, non flammable, in expensive easy to remove from the product and its Tc and Pc
are relatively low.
 Using CO2 as mobile phase even alow the extraction of thermally labile/ easily.
 Oxidisable compound even at low temperatures and non oxidant medium.
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Critical properties of various solvents
Solvent
s
Tc (K) Pc (MPa, atm) D(g/cm 3)
304.1 7.38 , 72.8 0.469
0 647.096 22.064,
217.755
0.322
190.4 4.60 , 45.4 0.162
305.3 4.87 , 48.1 0.203
369.8 4.25 (41.9) 0.217
282.4 5.04 (49.7) 0.215
364.9 4.60 (45.4) 0.232
512.6 8.09 (79.8) 0.272
513.9 6.14 (60.6) 0.276
508.1 4.70 (46.4) 0.278
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Table 1. Critical properties of various solvents
Table 2. Comparison of gases, supercritical
fluids and liquids.
Density
(kg/m3
)
Viscosity (
µPa·s)
Diffusivity
(mm2
/s)
Gases 1 10 1–10
Supercriti
cal fluids
100–1000 50–100 0.01–0.1
Liquids 1000 500–1000 0.001

Supercritical Fluids Extraction
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 Supercritical fluid extraction (SFE) is eco-friendly alternative of
extraction replacing organic solvents.
 In SFE use of supercritical fluids like supercritical as solvent is there.
 SCF helps in extraction of natural products of wide range of polarités.
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Supercritical fluid extraction (SFE):
continuous type :
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1.CO is compressed and heated to a supercritical
₂
state.
2.The supercritical CO is then pumped through an
₂
extraction vessel containing the material to be
extracted. The CO dissolves the desired compounds
₂
from the material, leaving behind the unwanted
impurities.
3. The CO and extracted compounds are then passed
₂
through a pressure reduction valve. This causes the
CO to expand and vaporize, leaving behind the
₂
extracted compounds.
4.The vaporized CO is then condensed and recycled
₂
for use in the next extraction cycle.
1
4
3
2

 Advantage :
 Enhanced transport properties—solute diffuses more rapidly through
a supercritical solvent than through a liquid solvent
 The solvent can be recovered as a gas by reducing the pressure, which offers the
prospect of significant energy saving
 There is greater flexibility in the process operating parameters of pressure and
temperature as compared with conventional liquid extraction processes.
 disadvantage :
 Its main disadvantages are the strong dependence on the matrix, mainly the
particle size, on the extraction efficiency, and the high cost of both the equipment.
 The disadvantage of SCFE is that the capital cost of a SCFE plant is substantially
higher (at least 50%) than a conventional extraction plant.
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Supercritical fluid chromatography
 Supercritical fluid chromatography (SFC) is a separation technique that
combines the principles of both gas chromatography (GC) and liquid
chromatography (LC) with the use of supercritical fluids as the mobile phase.
In SFC, carbon dioxide (CO2) is the most commonly employed supercritical
fluid, along with a co-solvent, to perform chromatographic separations.
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 three main types of chromatography based in the nature of mobile phase: gas
chromatography, liquid chromatography and super/subcritical chromatograph.
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 Chromatography is an important biophysical technique that enables the
separation, identification, and purification of the components of a mixture
for qualitative and quantitative analysis. It can also be used for the
separation of chiral compounds.
 SFC typically utilizes carbon dioxide as the mobile phase; therefore the entire
chromatographic flow path must be pressurized. SFC is used in industry
primarily for separation of chiral molecules, and uses the same columns as
standard high performance liquid chromatography systems.
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Fig 2: Schematic diagram of a supercritical fluid chromatograph designed for use
with packed columns
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Advantages and disadvantages of SFC:
 SFC is very clean; mobile phase contaminants are usually trace quantities of
other gases. The mobile phase is free of dissolved oxygen and is not
particularly reactive and the mobile phase is easily and rapidly removed. A
disadvantage of using carbon dioxide as the mobile phase is it does not elute
very polar or ionic compounds; this is overcome by using an organic modifier.
 However, there are some disadvantages of SFC these include that if molecules
are highly polar they are not soluble in the mobile phase. Usually SFC only
moves a small amount of a large specimen onto the column and has Limited
availability.
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Application:
 Decaffeination:
Methods for decaffeinating coffee have been available since the early 20th Century. The aim is to
remove caffeine without removing the compounds that give the coffee its flavour, and without leaving
a toxic residue in the beans
Several different solvents have been used:
Table 3: Types of solvents for decaffeination
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Fig 3: Decaffeination using supercritical carbon dioxide 18

conclusion
 In conclusion, supercritical fluid technology represents a remarkable and
versatile tool in various scientific disciplines and industries. Its ability to
efficiently separate and analyze complex mixtures, particularly in the fields
of pharmaceuticals, natural product research, environmental monitoring, and
more, has revolutionized the way we approach chromatography. By harnessing
the unique properties of supercritical fluids, we can achieve faster, more
selective, and environmentally friendly separations.
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